Heat Transfer - Engineering

Q1:

In sub-cooled boiling,

A temperature of the heating surface is less than the boiling point of the liquid.

B temperature of the heating surface is more than the boiling point of the liquid.

C bubbles from heating surface are absorbed by the mass of the liquid.

D very large vapour space is necessary.

ANS:B - temperature of the heating surface is more than the boiling point of the liquid.

In sub-cooled boiling, the temperature of the heating surface is more than the boiling point of the liquid. Sub-cooled boiling occurs when a liquid is heated above its boiling point but does not immediately boil. In this state, the liquid temperature is higher than its boiling point, but nucleation sites for boiling are not readily available. As a result, the liquid remains in contact with the heated surface at a temperature higher than its boiling point until enough energy is supplied to initiate boiling. Therefore, the correct statement is: "temperature of the heating surface is more than the boiling point of the liquid."